1. Field of the Invention
The invention relates to the technical field of an electric motor provided in a member device such as electrical equipment. More particularly, the invention provides a method and apparatus for fixing a brush holder to a holder stay.
2. Description of the Related Art
Generally speaking, some electric motors have feed members, such as brushes, brush holders within which the brushes movably fit, and a holder stay to which the brush holders are attached and fixed.
As shown in FIG. 1, some electric motors have a metal brush holder 2 with two pairs of fingers 2d formed to extend from both leg pieces 2b of the brush holder 2 so the fingers 2b face each other in parallel. The fingers 2d are then fixed to the holder stay 3 by first passing each finger 2d through a respective through hole 3c of the holder stay 3. The through holes 3c are slot-shaped and formed in an attachment surface section 3a of the holder stay 3. Each finger 2b is then bent along the back side of the attachment surface section 3a. As shown in FIG. 2, the fingers 2d are bent so that the fingers 2d face each other in a direction orthogonal to a longitudinal direction of the through holes 3c. In addition, the bent sections 2h of the fingers 2d are parallel to the longitudinal direction of the through holes 3c.
Although conventional holder stays are formed with resin material, such as, for example, Bakelite and other such plastics, some holder stays have attachment surface sections 3a that are made of metal. The attachment surface sections 3a are made of metal to increase heat resistance and heat dissipation. However, when the fingers 2d of the brush holders 2 are fixed to the holder stay as described above, the attachment surface section 3a of the holder stay 3 that is made of metal has a decreased frictional resistance and weak fixing power because metal parts are fixed to metal parts.
Attempts have been made to increase the fixing power of such a holder stay 3 by increasing the press load at the time the fingers are being fixed. However, since the attachment surface section 3a of the holder stay 3 is made of metal, the attachment surface section becomes thinner than when the holder stay 3 is made of plastic. In addition, the spring-back characteristic of metal then becomes a problem. As a result, the fixing power is not particularly increased even if the press load is increased. Additionally, there is a limit as to how much of a press load can be applied because there is a possibility of deforming the holder stay 3 under the large press load.